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Ignore automatically derived impls of Clone and Debug in dead code analysis

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This commit is contained in:
Fabian Wolff 2021-05-21 19:35:49 +02:00
parent 497ee321af
commit 79adda930f
54 changed files with 225 additions and 107 deletions
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62
compiler/rustc_passes/src/dead.rs
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@ -239,7 +239,69 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
}
}
/// Automatically generated items marked with `rustc_trivial_field_reads`
/// will be ignored for the purposes of dead code analysis (see PR #85200
/// for discussion).
fn should_ignore_item(&self, def_id: DefId) -> bool {
if !self.tcx.has_attr(def_id, sym::automatically_derived)
&& !self
.tcx
.impl_of_method(def_id)
.map_or(false, |impl_id| self.tcx.has_attr(impl_id, sym::automatically_derived))
{
return false;
}
let has_attr = |def_id| self.tcx.has_attr(def_id, sym::rustc_trivial_field_reads);
if has_attr(def_id) {
return true;
}
if let Some(impl_of) = self.tcx.impl_of_method(def_id) {
if has_attr(impl_of) {
return true;
}
if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of) {
if has_attr(trait_of) {
return true;
}
if let Some(method_ident) = self.tcx.opt_item_name(def_id) {
if let Some(trait_method) = self
.tcx
.associated_items(trait_of)
.find_by_name_and_kind(self.tcx, method_ident, ty::AssocKind::Fn, trait_of)
{
if has_attr(trait_method.def_id) {
return true;
}
}
}
}
} else if let Some(trait_of) = self.tcx.trait_of_item(def_id) {
if has_attr(trait_of) {
return true;
}
}
return false;
}
fn visit_node(&mut self, node: Node<'tcx>) {
if let Some(item_def_id) = match node {
Node::Item(hir::Item { def_id, .. })
| Node::ForeignItem(hir::ForeignItem { def_id, .. })
| Node::TraitItem(hir::TraitItem { def_id, .. })
| Node::ImplItem(hir::ImplItem { def_id, .. }) => Some(def_id.to_def_id()),
_ => None,
} {
if self.should_ignore_item(item_def_id) {
return;
}
}
let had_repr_c = self.repr_has_repr_c;
let had_inherited_pub_visibility = self.inherited_pub_visibility;
let had_pub_visibility = self.pub_visibility;